This invention relates to systems for the protection of secure areas, and to intruder detection systems. Specifically, it relates to an intruder detection system that can be integrated into a physical barrier and that is adapted to detect any physical deformation of the barrier.
It is often necessary to protect equipment and secure areas from unauthorized, unwanted and sometimes hostile personnel and vehicles. Such protection conventionally includes fencing that encompasses the area or equipment to be protected. Intruder detection systems are also used in conjunction with fences or other physical deterrent barriers to enable responsible personnel to monitor the premises and to take appropriate action in response to detected intrusions.
In U.S. Pat. No. 4,327,358, issued Apr. 27, 1982 to the present inventor, there is disclosed an integrated physical deterrent barrier and intruder detection sensor that provides surveillance of intrusions in the airspace over the barrier. The sensor is coextensive with and mounted on the top of the barrier and is integrated into a barbed wire topped chain link fence by arranging appropriately spaced parallel strands of barbed wire into a V configuration so as to form a corner reflector antenna at the system operating frequency. The active element of the corner reflecter is a leaky transmission line that extends the length of the corner reflector antenna, radiates RF energy and carries reflections from intrusion events back to a receiver and processing circuits.
While the aforementioned device has proven to be effective, it has been found to be susceptible to false alarms caused by birds and other non-target intrusions far above the physical barrier. Since it is a radiating device, it is also affected by the placement of objects in the vicinity of the device and furthermore it requires considerable power for its operation.